# US 2013/0153046 A1 · Electrostatic discharge protected ferrule

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- Number: US 2013/0153046 A1
- Document ID: US20130153046A1
- Status: Published application
- Kind: A1
- Application number: 13/327,850
- Filed: 2011-12-16
- Published: 2013-06-20
- Earliest claimed: 2011-12-16
- Assignees: The Boeing Company
- Inventors: Christopher Michael Hansom; James P. Irwin; Nathan Michael Kelley
- Web page: https://patentgrep.com/patent/US20130153046A1

## CPC

- F16L 39/005: {for concentric pipes}
- B64D 37/32: Safety measures not otherwise provided for, e.g. preventing explosive conditions
- B64D 45/02: Lightning protectors; Static dischargers
- F16L 13/0245: {with holes in the sleeve or spigot being filled with weld}
- F16L 13/103: {Adhesive joints}
- F16L 25/01: specially adapted for realising electrical conduction between the two pipe ends of the joint or between parts thereof
- F16L 25/025: {for joints with sleeve or socket}
- F16L 25/03: in non-disconnectable pipe joints
- F16L 47/03: Welded joints with an electrical resistance incorporated in the joint
- F16L 47/24: for joints between metal and plastics pipes
- Y02T 50/40: Weight reduction
- Y10T 137/0402: Cleaning, repairing, or assembling
- F16L: PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A fuel line assembly for an aircraft comprises a ferrule assembly comprising a ferrule affixed to an isolation tube, which may be directly affixed to a fuel tube or affixed to an extension tube, which in turn, is affixed to the fuel tube. The ferrule assembly provides electrostatic discharge protection and lightning protection as the isolation tube maintains a separation distance from the ferrule and fuel tube, both of which are made from metal. The isolation tube is made from a dielectric material, but which may have conductive particles added to aid in the dissipation of an electrostatic charge. The electrical resistance through the isolation tube has a lower limit to arrest the flow of the induced lightning current through the assembly. The amount of lightning protection afforded can be configured. The ferrule assembly components may be affixed by using thermo-welding, adhesive, or mechanical pressure.

## Claims

### Claim 1

A ferrule assembly comprising:
a ferrule comprising a cylindrical shape having a first end and a second end, the first end comprising a first lip and a second lip forming a channel configured to receive an O-ring; and
an isolation tube comprising non-metallic material configured to receive the second end of the ferrule, wherein the isolation tube is configured to receive a fuel tube and provide a separation distance between the fuel tube and the ferrule.

### Claim 2 (depends on 1)

The ferrule assembly of claim 1, wherein the isolation tube further comprises
an aluminum extension tube affixed to the isolation tube using an adhesive and is configured to provide the separation distance between the extension tube and the ferrule.

### Claim 3 (depends on 1)

The ferrule assembly of claim 1, wherein the ferrule is a metal ferrule and affixed to the isolation tube by one of an adhesion using an adhesive, thermo-welding, or spin welding.

### Claim 4 (depends on 2)

The ferrule assembly of claim 2, wherein the extension tube is affixed to the isolation tube by one of adhesion using an adhesive, thermo-welding, or spin welding.

### Claim 5 (depends on 1)

The ferrule assembly of claim 1, wherein the isolation tube comprises a first inner band and a first outer band, wherein the first inner band and the first outer band form a groove for receiving the second end of the ferrule.

### Claim 6 (depends on 5)

The ferrule assembly of claim 5, wherein the isolation tube comprises a second inner band and a second outer band, wherein the second inner band and the second outer band from a second groove configured to receive the fuel tube.

### Claim 7 (depends on 2)

The ferrule assembly of claim 2, wherein the isolation tube comprises a second inner band and a second outer band, wherein the second inner band and the second outer band from a second groove configured to receive the extension tube.

### Claim 8 (depends on 1)

The ferrule assembly of claim 1, wherein the ferrule comprises metal and further comprises a body section comprising a plurality of holes on a side wall of the ferrule.

### Claim 9 (depends on 8)

The ferrule assembly of claim 8, wherein the holes on the side wall of the ferrule are filled by material of the isolation tube forming a mechanical lock.

### Claim 10 (depends on 1)

The ferrule assembly of claim 1, wherein the fuel tube comprises metal and further comprises a body section comprising a plurality of holes on a side wall of the fuel tube.

### Claim 11 (depends on 10)

The ferrule assembly of claim 10, wherein the holes in the fuel tube are filled by material of the isolation tube forming a mechanical lock.

### Claim 12 (depends on 1)

The ferrule assembly of claim 1, wherein the extension tube comprises metal and further comprises a body section comprising a plurality of holes on a side wall of the extension tube.

### Claim 13 (depends on 8)

The ferrule assembly of claim 8, wherein the isolation tube comprises PEEK or PEKK.

### Claim 14 (depends on 13)

The ferrule assembly of claim 13, wherein the isolation tube and the extension tube is rendered conductive by adding conductive filler to provide electrostatic conductivity, wherein the electrostatic conductivity is used to control the electrical resistance to fall within a permissible range through the isolation tube from the ferrule to the extension tube or fuel tube.

### Claim 15 (depends on 1)

The ferrule assembly of claim 1, wherein the separation distance is at least 0.2 inches and is configured to withstand a flashover through air from the ferrule to either the extension tube or the fuel tube at 400 volts at 40,000 feet.

### Claim 16 (depends on 1)

The ferrule assembly of claim 1, wherein the separation distance is at least 3 inches and is configured to withstand a flashover through air from the ferrule to either the extension tube or the fuel tube at 5000 volts at 40,000 feet.

### Claim 17 (depends on 13)

The ferrule assembly of claim 13, wherein the isolation tube comprising PEEK or PEKK (or any other suitable material) is rendered conductive by adding conductive filler to provide electrostatic conductivity.

### Claim 18 (depends on 17)

The ferrule assembly of claim 17, wherein the conductive filler is used to control electrical resistance so as to fall within a permissible range through the isolation tube from the ferrule to either the extension tube or the fuel tube.

### Claim 19 (depends on 18)

The ferrule assembly of claim 18, wherein the permissible range of the electrical resistance through the isolation tube does not exceed an upper limit of 100 mega-ohms.

### Claim 20 (depends on 18)

The ferrule assembly of claim 18, wherein the lower limit of the permissible range of the electrical resistance through the isolation tube is not less than 8,000 ohms at 400 volts when the separation distance is at least 0.2 inches.

### Claim 21 (depends on 18)

The ferrule assembly of claim 18, wherein the lower limit of the permissible range of the electrical resistance through the isolation tube is not less than 100,000 ohms at 5000 volts when the separation distance is at least 3 inches.

### Claim 22

A fuel tube connection assembly comprising:
a cylindrically shaped ferrule having a first end and a second end, the first end comprising a first lip and a second lip forming a channel configured to receive an O-ring;
an isolation tube comprising a non-conductive material having a tubular shape affixed to the second end of the ferrule; and
a fuel tube affixed to the isolation tube, wherein the isolation tube provides a separation distance between the fuel tube and the ferrule configured to prevent an arc between the fuel tube and the ferrule, wherein an electrostatic conductivity of the isolation tube is determined in part by a conductive filler added to the isolator tube to provide an electrical resistance between the fuel tube and the ferrule.

### Claim 23 (depends on 22)

The fuel tube connection assembly of claim 22, wherein the isolation tube comprises a least one of carbon, glass or Kevlar fiber material.

### Claim 24 (depends on 23)

The fuel tube connection assembly of claim 23, wherein the isolation tube is affixed to the fuel tube by one of adhesion using an adhesive, spin welding, thermo-welding, or swaging.

### Claim 25 (depends on 24)

The fuel tube connection assembly of claim 24, wherein the separation distance of at least 0.2″ is provided.

### Claim 25 (depends on 24)

The fuel tube connection assembly of claim 24, wherein the isolation tube is affixed by adhesion and the adhesive comprises either metal particles or carbon black for dissipating a static charge.

### Claim 26 (depends on 24)

The fuel tube connection assembly of claim 24, wherein the fuel tube has a larger diameter at an end of the fuel tube configured to receive the isolation tube.

### Claim 27 (depends on 24)

The fuel tube connection assembly of claim 24, wherein the isolation tube has an electrical resistance that falls within the range of 8KΩ to 100KΩ.

### Claim 29

A method of installing fuel lines in an aircraft comprising the operations of:
affixing an isolation tube to a first fuel tube;
affixing a ferrule to the isolation tube;
installing the first fuel tube section in a structure of the aircraft; and
affixing the ferrule to a fuel system component, wherein any of the first three operations can be performed in any order.

### Claim 30 (depends on 23)

The method of claim 23, wherein affixing the ferrule to the fuel system component comprises affixing the ferrule to a coupler and affixing a second fuel tube to the coupler.

### Claim 31 (depends on 23)

The method of claim 23, wherein affixing the ferrule to the isolation tube comprises either
thermo-welding or spin welding the ferrule to the isolation tube, or
using an adhesive to affix the ferrule to the isolation tube.